Type of nervous system • Type of nervous system determines rate of creation of new conditioned reflexes, strength and stability of these reflexes, intensity of external and internal inhibition, rate of irradiation and concentration of nervous processes, the capacity for induction and less or grater possibility for development of abnormalities of higher nervous activity.
Type of nervous systemafter I.P. Pavlov I.P. Pavlov classifies types of higher nervous activity according to several attributes that considered as most reliable indices of higher nervous activity. These were intensity of the excitation and inhibition, the ratio of these processes in central nervous system and their mobility, that is rate at which excitation was replaced by inhibition and wise versa. In experimental practice the following four principle types of higher nervous activity are met: • 1) strong unbalanced type, characterized by predominance of excitation over inhibition; • 2) strong well-balanced active type, characterized by high mobility of nerve processes; • 3) strong well-balanced passive type, characterized by low mobility of nerve processes; • 4) weak type, characterized by extremely weak development of both excitation and inhibition, which cause fatigue and low workability.
The first and second signaling system • The analysis and synthesis of the direct stimuli from surroundings first signal system performs. This includes impressions, sensations. This functional mechanism is common in human and animals. In the course of his social development and labor activity second signal system, which based on using verbal signals, develop. This system includes perception of words, reading and speech. • The development of the second signaling system was incredibly broadened and changed quality of higher nervous activity of cerebral hemispheres. Words are signals of other signals. Man uses verbal signals for everything he perceives through the receptors. Words are abstraction of reality and allow generalization, processing of surrounding primary information. This gives the first general human empiricism and finally science, the instrument of man's higher orientation in the environment and its own self. • So, second signaling system is socially determined. Outside the society, without association with other people second signaling system is not developed.
Nerve substrate of speech • There are two aspects of communication: sensory, involving reading, hearing of speech, and second, the motor aspect, involving vocalization and its control. It is known, that lesion of posterior portion of the superior temporal gyrus, which is called Wernicke's area, and is part of auditory associative cortex, make impossible to the person to interpret the meanings of words. This Wernicke's area is located in dominant hemisphere, which is usually the left. The process of speech includes two principle stages of mentation: formation of thoughts to be expressed and motor control of vocalization. The formation of thoughts is the function of associative areas in the brain. Wernicke's area in the posterior part of the superior temporal gyrus is most important for this ability. Broca's speech area lies in prefrontal and premotor facial region in the left hemisphere. The skilled motor patterns for control of the larynx, lips, mouth, respiratory system and other accessory muscles of speech are all initiated from this area. Articulation means movements of mouth, tongue, larynx, vocal cords, and so forth that are responsible for the intonations, timing, and rapid changes in intensities of the sequential sounds. The facial and laryngeal regions of the motor cortex activate these muscles, and the cerebellum, basal ganglia, and sensory cortex all help control the sequences and intensities of muscle contractions. Transmitters such as dopamine, noradrenaline, serotonin and certain neuropeptides transmit their signals by what is referred to as slow synaptic transmission. The resulting change in the function of the nerve cell may last from seconds to hours. This type of signal transmission is responsible for a number of basal functions in the nervous system and is of importance for e.g. alertness and mood. Slow synaptic transmission can also control fast synaptic transmission, which in turn enables e.g. speech, movements and sensory perception.
Development of signaling systems in children • The ability of a full-term baby to develop temporary connections of the first signaling system arises in a few days after the birth.. In the first six months of life speech sounds mean little to a child. They are simply stimuli to the auditory analyzer like any other sounds. • The first signs of development of the second signaling system appear during the second half of the first year of life. If a person or an object is named and shown to a child many times, reaction to this name develops. • Later after leaning a few words, a child begins to name objects itself. Finally, at a later time he uses a stock of words to communicate with other people.
Functions of speech • Main functions of speech are communicative, regulatory, programming and gives general notion about surroundings. Communicative function permits exchange of information between people. Such a function is also present in animals, which use for this aim vocalization of different intensity to warn about danger or express positive and negative emotions. People use verbal signals for everything he perceives through the receptors. Words are abstraction of reality and allow generalization, processing of surrounding primary information. • Verbal instructions may direct human activity, give suggestion about proper mode of behavior. This is programming function of speech. Programming function of speech involves emotional component also, which may influence to emotional status of a person. As limbic system, which controls emotions, has direct connection with autonomic nervous system. • So speech through emotions may influence to functions of visceral organs. Physician may use this effect for psychotherapy. It is necessary remember about jatrogenic disorders also.
Attention as psychical function • Attention is selectiveness of psychical processes or any kind of mental activity, which helps in getting and processing the information. There are sensory, motor, intellectual and emotional forms of attention, depending to kind of activity of a person. • There are voluntary and involuntary levels of attention. Involuntary attention is present from the birth of man. Voluntary attention develops in life course, due to mental activity, formation of speech function and studying languages.
Physiological mechanisms of attention • Involuntary attention is controlled by lower portion of brain stem and midbrain, where centers of roof reflexes are locates. Voluntary attention appears as a result of higher cortical activity in visual, auditory, motor areas and so on. • Lesion of these cortical areas leads to such disturbances in processing special sensory information as ignore of stimuli of different modality. Intellectual attention appears because of function of prefrontal associative cortical area. The limbic system of the brain is responsible for emotional attention.
Memory as psychical function • Memory function helps fixing of perceived information, keeping it in verbal form or as traces of percept stimuli and recognizing of this information in proper time. Genetic memory keeps information about body structure and forms of its behavior. Biological memory is presented in both philogenetic and ontogenetic forms. The immune memory and psychical memory for instance, belong to ontogenetic memory. • General characteristics of memory are duration, strength of keeping the information and exactness of its recognizing. In man mechanisms of perception and keeping the information are developed better, comparing to other mammalians. • According to duration is concerned short-time and long-time memory; in relation to kind of information – sensory and logic.
Thinking process as psychical function • The prefrontal association area is essential to carrying out thought processes in the mind. This presumably results from some of the same capabilities of the prefrontal cortex that allow it to plan motor activities. • The prefrontal association area is frequently described as important for elaboration of thoughts to store on a short-term basis “working memories” that are used to analyze each new thought while it is entering the braine. The somatic, visual, and auditory association areas all meet one another in the posterior part of the superior temporal lobe. This area is especially highly developed in the dominant side of the brain – the left side in almost all right-handed people. • It plays the greatest single role of any part of cerebral cortex in the higher comprehensive levels of brain function that we call intelligence. This zone is also called general interpretative area, the gnostic area, the knowing area, tertiary association area. It is best known as Wernike’s area in honor of the neurologist who first describes it.
Nerve substrate of memory • It’s discovered the nervous substrate of long-term memory is mostly cerebral cortex. The most important regions are temporal lobes, prefrontal area and hippocampus. Experimental researches revealed that some thalamic nuclei and reticular formation take part in memory function. • Reticular formation gives ascending stimulatory influences to cerebral cortex, which help in keeping awake condition of cortex and provides voluntary attention.
Physiological mechanisms of memory • At the molecular level, the habitation effect in the sensory terminal results from progressive closure of calcium channels through the presynaptic terminal membrane. • In case of facilitation, the molecular mechanism is believed to be following. Facilitated synapse releases serotonin that activates adenylyl cyclase in postsynaptic cell. Then cyclic AMP activates proteinkinase that then causes phosphorylation of proteins. This blocks potassium channels for minutes or even weeks. Lack of potassium causes prolonged action potential in the presynaptic terminal that leads to activation of calcium pores, allowing tremendous quantities of calcium ions to enter the sensory terminal. This causes greatly increased transmitter release, thereby markedly facilitating synaptic transmission. • Thus in a very indirect way, the associative effect of stimulation the facilitator neuron at the same time that the sensory neuron is stimulated causes prolonged increase in excitatory sensitivity of the sensory terminal, and this establishes the memory trace.
Short and long term memory • Eric Kandel showed initially that weaker stimuli give rise to a form of short term memory, which lasts from minutes to hours. The mechanism for this "short term memory" is that particular ion channels are affected in such a manner that more calcium ions will enter the nerve terminal. This leads to an increased amount of transmitter release at the synapse, and thereby to an amplification of the reflex. This change is due to a phosphorylation of certain ion channel proteins, that is utilizing the molecular mechanism described by Paul Greengard. • A more powerful and long lasting stimulus will result in a form of long term memory that can remain for weeks. The stronger stimulus will give rise to increased levels of the messenger molecule cAMP and thereby protein kinase A. These signals will reach the cell nucleus and cause a change in a number of proteins in the synapse. The formation of certain proteins will increase, while others will decrease. The final result is that the shape of the synapse can increase and thereby create a long lasting increase of synaptic function. • In contrast to short term memory, long term memory requires that new proteins are formed. If this synthesis of new proteins is prevented, the long term memory will be blocked but not the short term memory.
Consciousness and its mechanisms • Consciousness is special form of perceiving surroundings and goal-orientated activity of person with interrelation to surroundings. Only social life forms consciousness. It involves life experience of entire society. • This ability of prefrontal areas to keep track of many bits of information could well explain abilities to prognosticate, do plan for the future, delay action in response to incoming sensory signals, consider the consequences of motor actions even before they are performed, solve complicated mathematical, legal, or philosophical problems, correlate all avenues of information in diagnosing rare diseases and control our activities in accord with moral laws.
Notion “emotions” • Emotions are aspect of higher nervous activity that characterize subjective attitude of person to various stimuli arousal in surroundings. • Emotional status reflects actual needs of man and helps in its realization.
Classification of emotions • According to subjective status there are positive and negative emotions. Negative emotions are sthenic (aggression, affect) that stimulate human activity and asthenia (horror, sadness, depression) that inhibit behaviour. Lower or elementary emotions are caused by organic needs of man or animal as hanger, thirst and survival, so on). • In humans even lover emotions undergo to cortical control and are brining up. Social, historical and cultural customs cause also formation of higher emotions that regulates public and private relations in society. Higher emotions appear due to consciousness and may inhibit lower emotions.
Appearance of emotions in ontogenesis • In newborns emotions of horror, anger, pleasure, are revealed just after birth. Hunger, pain, getting cool, wet bedclothes cause in newborn child negative emotions with grimace of suffering and crying. Sudden new sound or loss equilibrium causes horror and loss of free movement causes anger. • Final formation of human emotions develops gradually with maturation of nervous and endocrine regulatory systems and needs up brining.
Biological importance of emotions • Emotions are important element of human behaviour, creation of conditioned reflexes and mentation. • Negative emotions give fusty evaluation of current situation does it useful or not. Mobilizing of efforts helps then to satisfy current needs of person. • Positive emotions help to put in memory scheme of behaviour, which was useful and have lead to success.
External manifestations of emotions • Motor manifestations of emotions are mimic, gesticulation, body posture and walk. • Emotional excitation usually is followed by autonomic reactions as blush, dilation of pupils; increase of arterial pressure, rate of heartbeat and breathing. Level of catecholamines in blood and 17-oxycetosteroides in urine rises also. • Positive emotion may activate parasympathetic division of autonomic nervous system. Severe emotional excitation may result in visceral disorders because of circulatory disturbances and excess hormones in blood.
Nerve substrate of emotions • Several limbic structures are particularly concerned with the affective nature of sensory sensations – that is whether the sensations are pleasant or unpleasant. The major rew3ard centres have been found to be located along the course of the medial forebrain bundle, especially in the lateral and ventromedial nuclei of the hypothalamus. • Less potent reward centres are found in the septum, amygdala, certain areas of the thalamus, basal ganglia, and extending downward into the basal tegmentum of the mesencephalon. The most potent areas for punishment and escape tendencies have been found in the central grey area surrounding the aqueduct of Sylvius in the mesencephalon and extending upward into the periventricular zones of the hypothalamus and thalamus. • Less potent punishment areas are found in some locations in the amygdala and the hippocampus. Electrical recording from the brain show that newly experienced types of sensory stimuli almost excite areas in the cerebral cortex.
Theories of emotions • Biological theory of emotions (P.K. Anochkin) considers that life course includes two main stages of behavioural act: 1) formation of needs and motivations that results from negative emotions and 2) satisfaction of needs that leads to positive emotions it case of complete accordance of image and result of action. Incomplete compliance of suspected and real result of action cause negative emotions and continues behavioural act. • Information theory of emotions (P.V. Simonov)considers that emotions reflect strength human of need and possibility of its satisfaction in current moment. In absence of needs emotions can’t arise. There is also not emotional excitation, if getting excess information about mode of satisfaction this need. Lac of information already causes negative emotions that help to recall to mind life experience and to gather information about current situation.
Neurotransmission of emotional excitation • Emotional excitation is spread in the brain due to variety of neurotransmitters (noradrenalin, acetylcholine, serotonin, dopamine and neuropeptides including opioides. • Positive emotions may be explained by revealing catecholamines and negative emotions, aggression result from production acetylcholine in the brain. Serotonin inhibits both kinds of emotions. • Decrease of serotonin in blood is followed by groundless anxiety and inhibition of noradrenergic transmission results in sadness.
Structure of behavioural act According to theory of functional systems (Anochking) there are such stages of behavioural act: • 1) afferent synthesis; 2) taking of decision; • 3) acceptor of result of action; • 4) efferent synthesis (or programming of action); • 5) performing of action; • 6) evaluation of final result of action. • Due to converging and processing of both sensory information and memory traces afferent synthesis in the brain is performed. Taking of decision is based on afferent synthesis by choosing optimal variant of action.
Neuronal mechanisms of behaviour • In the very lowest animals olfactory cortex plays essential roles in determining whether the animal eats a particular food, whether the smell of a particular object suggest danger, and whether the odour is sexually inviting, thus making decisions that are of life-or-death importance. The hippocampus originated as part of olfactory cortex. • Very early in the evolutionary development of the brain, the hippocampus presumably becomes a critical decision-making neuronal mechanism, determining the importance of the incoming sensory signals. Once this critical decision-making capability had been established, presumably the remainder of the brain began to call on it for the same decision making. Therefore, if the hippocampus says that a neuronal signal is important, the information is likely to be committed to memory. • Thus, a person rapidly become habituated to indifferent stimuli but learns assiduously any sensory experience that causes either pleasure or pain. It has been suggested that hippocampus provides the drive that causes translation of short-term memory into long-term memory.